There is a technique for electronic devices equipped with an object to be cooled and a cooling fan for cooling the object, as referred to in Japanese Patent Publication No. JP-A-2007-73707, by controlling the operation of the cooling fan according to a temperature measured by a thermistor disposed in the vicinity of the object.
However, this technique may create certain problems. For example, if a relatively large amount of dust is adhered to an air filter attached to the intake port of the outer casing, the quantity of air that is taken to the interior through the air filter and sent to the object is decreased. This causes a large difference between the temperature of the object (the temperature of the object (a liquid crystal panel) which is increased by the irradiation of light emitted from a light source unit) and the temperature in the vicinity of the object. The rotation speed of the cooling fan is set according to the temperature in the vicinity of the object, which is lower than that of the object, even though the object has high temperature, because the technique of JP-A-2007-73707 controls the operation of the cooling fan according to the temperature in the vicinity of the object. This can lead to problems of not cooling the object appropriately.